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Neutron diffraction data obtained on single crystals of PbZr1-xTixO3 with x = 0.325 and x = 0.460, which lie on the pseudorhombohedral side of the morphotropic phase boundary, suggest a coexistence of rhombohedral (R3m/R3c) and monoclinic (Cm) domains and that monoclinic order is enhanced by Ti substitution. A monoclinic phase with a doubled unit cell (Cc) is ruled out as the ground state.
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Based on the relativistic spin-polarized density functional theory calculations we investigate the crystal structure, electronic and magnetic properties of a family MnPn2Ch4 compounds, where pnictogen metal atoms (Pn) are Sb and Bi; chalcogens (Ch) are Se, Te. We show that in the series the compounds of this family with heavier elements prefer to adopt rhombohedral crystal structure composed of weakly bonded septuple monoatomic layers while those with lighter elements tend to be in the monoclinic structure. Irrespective of the crystal structure all compounds of the MnPn2Ch4 series demonstrate a weak energy gain (of a few meV per formula unit or even smaller than meV) for antiferromagnetic (AFM) coupling for magnetic moments on Mn atoms with respect to their ferromagnetic (FM) state. For rhombohedral structures the interlayer AFM coupling is preferable while in monoclinic phases intralayer AFM configuration with ferromagnetic ordering along the Mn chain and antiferromagnetic ordering between the chains has a minimum energy. Over the series the monoclinic compounds are characterized by substantially wider bandgap than compounds with rhombohedral structure.
The first observation of microwave magnetoelectric (ME) interactions through ferromagnetic resonance (FMR) in bilayers of single crystal ferromagnetic-piezoelectric oxides and a theoretical model for the effect are presented. An electric field E produces a mechanical deformation in the piezoelectric phase, resulting in a shift dHE in the resonance field for the ferromagnet. The strength of ME coupling is obtained from data on dHE vs E. Studies were performed at 9.3 GHz on bilayers of (111) yttrium iron garnet (YIG) films and (001) lead magnesium niobate-lead titanate (PMN-PT). The samples were positioned outside a TE102-reflection type cavity. Resonance profiles were obtained for E = 0-8 kV/cm for both in-plane and out-of-plane magnetic fields H. Important results are as follows. (i) The ME coupling in the bilayers is an order of magnitude stronger than in polycrystalline composites and is in the range 1-5.4 Oe cm/kOe, depending on the YIG film thickness. (ii) The coupling strength is dependent on the magnetic field orientation and is higher for out-of-plane H than for in-plane H. (iii) Estimated ME constant and its dependence on volume ratio for the two phases are in good agreement with the data.
Renewed interest has been witnessed in utilizing the piezoelectric response of $PbZr_{0.52}Ti_{0.48}O_{3}$ (PZT) films on glass substrates for applications such as data storage and adaptive optics. Accordingly, new methodologies are being explored to grow well-oriented PZT thin films to harvest a large piezoelectric response. However, thin film piezoelectric response is significantly reduced compared to intrinsic response due to substrate induced clamping, even when films are well-oriented. Here, a novel method is presented to grow preferentially (100)-oriented PZT films on glass substrates by utilizing crystalline nanosheets as seed layers. Furthermore, increasing the repetition frequency up to 20 Hz during pulsed laser deposition helps to tune the film microstructure to hierarchically ordered columns that leads to reduced clamping and enhanced piezoelectric response evidenced by transmission electron microscopy and analytical calculations. A large piezoelectric response of 280 pm/V is observed in optimally tuned structure which almost triples the highest reported piezoelectric response on glass. To confirm that the clamping compromises the piezoelectric response, denser films are deposited using a lower repetition frequency and a $BiFeO_{3}$ buffer layer resulting in significantly reduced piezoelectric responses. This paper demonstrates a novel method for PZT integration on glass substrates without compromising the large piezoelectric response.
Previous studies of Barkhausen noise in PZT have been limited to the energy spectrum (slew rate response voltages versus time), showing agreement with avalanche models; in barium titanate other exponents have been measured acoustically, but only at ambient temperatures. In the present study we report the Omori exponent (-0.95$pm$0.03) for aftershocks in PZT and extend the barium titanate studies to a wider range of temperature.
The effect of polarization fatigue on the Rayleigh coefficients of ferroelectric lead zirconate titanate (PZT) thin film was systematically investigated. It was found that electrical fatigue strongly affects the Rayleigh behaviour of the PZT film. Both the reversible and irreversible Rayleigh coefficients decrease with increasing the number of switching cycles. This phenomenon is attributed to the growth of an interfacial degraded layer between the electrode and the film during electrical cycling. The methodology used in this work could serve as an alternative non-destructive way for evaluating the fatigue endurance and degradation in dielectric properties of ferroelectric thin-film devices during applications.
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